内蒙古维拉斯托锡多金属矿床流体包裹体及其对成矿的指示

维拉斯托位于中亚造山带东部的大兴安岭以南,成型的锡成矿带主要在我国南岭,大兴安岭是我国北方的锡成矿地区。矿床成矿阶段包括斑岩体内的Ⅰ天河石化-钠长石化阶段、Ⅱ云英岩阶段、Ⅲ隐爆角砾岩阶段和Ⅳ晚期硫化物阶段。流体包裹体研究显示,流体包裹体的类型以液相为主的两相包裹体较多,而还存在以气相为主的两相包裹体,含子晶的三相包裹体和H_(2)O-CO_(2)包裹体,此三类数目较少。Ⅰ天河石化-钠长石化阶段均一温度为358~463℃,盐度为4.7%~8.6%NaCleqv,密度为0.46~0.71 g/cm^(3);Ⅲ隐爆角砾岩阶段均一温度为233~318℃,盐度为3.55%~10.61%NaCleqv,密度为0.77~0.87 g/cm^(3);Ⅳ晚期硫化物阶段均一温度为247~300℃,盐度为6.88%~7.93%NaCleqv,密度为0.85~0.86 g/cm^(3)。对矿物所含包裹体显微测温分析结果成矿流体具中高温、低盐度、中密度的性质,推测为同源流体来源及其演化。早期的基性-超基性岩浆演化携带成矿元素之后与深源岩浆混合一起形成成矿流体,成矿流体冷却是锡矿成矿的原因。

The Weilasituo Sn-polymetallic deposit is located in the south of the Great Xing'an Range in the east of Central Asian orogenic belt,and the formed tin metallogenic belt is mainly in Nanling of China.The Great Xing'an Range is a tin metallogenic area innorthern China.The metallogenic stages of the deposit include Iamazonite-albite petrochemical stage in porphyry,Ⅱ greisen stage,Ⅲ cryptoexplosive breccia stage and Ⅳ Late sulfide stage.The study of fluid inclusions shows that there are many types of fluid inclusions,including liquid-phase two-phase inclusions,gas-phase two-phase inclusions,daughter-containing three-phase inclusions and H_(2)O-CO_(2) inclusions,but the number of these three types is small.The homogenization temperature of Iamazonite-albitepetrochemical stage varies from 358 to 463.3℃,with the salinity of 4.7%~8.6%NaCleqv and the density around 0.46~0.71 g/cm^(3);the Ⅲ fluid inclusions from cryptoexplosive breccia exhibit a homogenization temperature range of 232.6~318.2℃,with salinity and density of 3.55%~10.61%NaCleqv and 0.77~0.87 g/cm^(3);the Ⅳ homogenization temperature in the sulfide stage is 246.8~300.4℃,the salinity is 6.88%~7.93%NaCleqv,and the density is 0.85~0.86 g/cm^(3).Micro-thermometric analysis of inclusions in minerals shows that the ore-forming fluid has the properties of medium-high temperature,low salinity and medium density,which is presumed to be the source and evolution of homologous fluid.The early evolution of basic-ultrabasic magma carried ore-forming elements and then mixed with deep magma to form ore-forming fluid,and the cooling of ore-forming fluid was the cause of tin mineralization.